Lateral thrust rudders are known in which a water conveying mechanism for producing a thrust, for example, a propeller, is supported in a cross-channel which extends from one side of the ship to the other. Also, lateral thrust rudders are known in which the channel system is T-shaped, the water being sucked in for example at the bottom of the ship or at the bow and ejected selectively to one side or the other. These lateral thrust rudders are used to give the ship a lateral thrust, depending on the direction in which the water is ejected from the cross-channel, in order to make maneuvering of the ship easier. Lateral thrust rudders are also known in which the channel openings can be closed off with hatches.
The end openings of conventional cross-channels which extend from one side of the ship to the other serve, due to the necessary change in the water flow direction, at one time as an inlet and at another time as an outlet. Even though an inlet should ideally be shaped differently than an outlet to facilitate the water flow, both channel ends must in practice always have the same shape and size. Thus, the water cannot be accelerated within the cross-channel, but must receive its necessary acceleration during entrance to the channel on the suction side of the propeller. In addition to the poor propeller efficiency which results, there exists a danger of air penetration causing a sudden interruption of the thrust force, cavitation, and all common side effects. Further, the thrust force decreases rapidly with increasing speed of the ship and stops completely during moderate travel of the ship, due to the ejector or suction action of the bypassing water. Similar disadvantages are present in conventional lateral thrust rudders having a T-shaped channel system.
The basic purpose of the invention is therefore to avoid the foregoing disadvantages and, in particular, to improve efficiency and to avoid or at least strongly reduce cavitation.